Working bacwards

[Michael Murphy]

Hi guys, I got a lot of good advice and feed back from the Titan Tuba forum and Im sure Ill also get from here.
Ive built 2 of the 4 Titan 39's x 30"wide, I just ordered 2 OT12 from leyland, so my first small herd is 4T39's + 2 OT12
I have six QSC1400 amps
We use laptops for source sound presently with virtual dj, but also have pioneer cd mixer and music files from laptop
Presently I dont need stereo sound but would like to factor it in for expansion of the tops
So weve got the cabs, amps and source
I need eq and limiters and HP,LP points for bass and tops cabs
Now the big question
What other gear do I need, what models etc and how to hook them up in what order, cause ive scanned the forums and have not gotten a difinitive direction.
Let me built it through your eyes! and ears

[Grant Bunter]

Hi pumpsfast,

Remind us what you have driver wise in your T39's, and what you plan to have in your OTops.

I seem to get into trouble making suggestions about amps, but your QSC amps look a bit light on power output. 2 of them might be good for your Otops (with your eventual plan to run in stereo).
Bridging is not a preferred option (and only let's you drive 1 cab per amp) , running 2 x T39's on one channel only of 1 of your QSC's will net you 42V output.

Another option is to sell off 4 of the QSC's for something a bit more powerful, or keep them for other projects, and buy a couple of new higher powered amps.

There's a number of DSP/Crossove/limiterr options and EQ options.
The DBX Driverack series have a quality name and will do all you want.

Plenty of us use the Behringer DCX 2496 DSP unit, combined with the DEQ 2496 for EQ/RTA.
I use this combo and have had no hitches to date that have been attributable to the units.
I crossover at 95Hz to tops.
While you can also EQ with the DCX, it seems to rapidly chew up available processor room.

For less than 4 x T39's, the high pass is 45Hz, and with 4 or more, 40Hz.
I low pass at 95Hz.

There's also offerings from BBE and Bunker Audio

That's a start and hope this helps...

[Michael Murphy]

Hey Grant, thought of contacting you for advice but thought id create a post for the greater benefit of the group, but glad you responded.
Leyland said he is going to use the Deltalite 2512 driver, and I got a great discount on ordering 6 lab 12's from him, so the T39s will be lab loaded

So Ive got 2 of the T39's built, target 4 V plated HP @ 40hz. Was thinking of LP @ 100hz but the 95hz is close on target. Id have to hear the OT12's to determine ultimate value, maybe some one already has these cabs and has some values too.

Amp wise yes it seems to be a lil under powered for the subs, im not worried right now though Id like to run them on the QSC1400, http://media.qscaudio.com/pdfs/disconti ... s/1400.pdf, and measure voltage db etc. I have a QSC 2050 I can step up to compare max db at max voltage limit
The Lab 12 is limited at 50V and it being a 6ohm +2ohm from the cab= 8ohm plugging in 50V and 8ohms into, http://www.sengpielaudio.com/calculator-ohm.htm
nets 312.5 watts, If I use 1amp per sub rated 270W@8ohms continous theoretically im short on power. Real world we will see
Whats the Voltage limit for the Deltalite 2512?
Oh I know its not reccomended, bridging, but with a stone wall limiter wont this stop me from blowing a driver?

Lets get going

[Grant Bunter]

This is Bill's take on bridging:
http://billfitzmaurice.info/forum/viewt ... =6&t=19292, as well as what's in the plans.

The 2510 is also used in the DR250, IIRC it's limit is something like 44.7V. Someone here is limiting the DR's down to 38V. The Otops will be 1-2dB down in output compared to the DR250, but I reckon that 38-40V is a good target, so you can put that into your calculator and work from there.

I can't find specs on the other QSC amp you mentioned, but I know you want 625W into 4 ohms to get 50V with 2 x T39 cabs parallel wired.

You're right though, loud is loud lol.
I still haven't got my BP102 loaded cabs to war volume (which are limited to 35V), but I'm doing live music.
You're just robbing yourself of what you can get out of your cabs, since you spent the money on the labs.

Tell me, are you running your laptop(s) into a mixer? Or have you got headphone output to line level adaptors?
Somewhere along the way you need to be able to adjust gain to below clipping...

[biggerrigger]

Grant is right on par with the 38v-40v limit. After setting up your stack of T39's and DR250's you will probably find that you are no where close to the 38v's for the 250's after you set up your system. I for one was quite shocked to see that I was only running 18v's trough my 4 DR250's compared to the output that I was hearing out of them. They are very loud and clean on very little power.

[Michael Murphy]

Hey biggerrigger (thought there was a bigrigger also) figured you would chime in only waiting on synwave and it hertz now.
To clear some thing up the tops from leyland are OT12, dont know where grant got to the DR250. So that being said whats the voltage limit for the deltalite 2512.
To answer Grant yes some times we run 3.5 I think it is to RCF out, but ideally it will go via usb to the mixer.
OK concider me to be a complete newbie. When setting up in order of signal flow it will be
1. Source - Lap top, cd players, android phones etc
2. Mixer
3. DSP
3.5 Eq
4. Limiter
5. Amps
6. Cabs

Is this correct?
And correct me if im wrong a 6db gain equateds to double the sound level, i.e double spl
And that being said if the max volatge on using one channel on the QSC 1400 per sub 8ohms 270 watts = 46Volts and 50V being the limit for the lab12 that 4V less is equal to what interms of db. I saw sinewave some where calculate this, but cant find it again.

And biggerrigger what your saying is that I will most likley be sending a lot less than peak voltage to the OT12's to balance the bass and tops?

[Grant Bunter]

Hey biggerrigger (thought there was a bigrigger also) figured you would chime in only waiting on synwave and it hertz now.
To clear some thing up the tops from leyland are OT12, dont know where grant got to the DR250. So that being said whats the voltage limit for the deltalite 2512.
To answer Grant yes some times we run 3.5 I think it is to RCF out, but ideally it will go via usb to the mixer.
OK concider me to be a complete newbie. When setting up in order of signal flow it will be
1. Source - Lap top, cd players, android phones etc
2. Mixer
3. DSP
3.5 Eq
4. Limiter
5. Amps
6. Cabs
Is this correct?
And biggerrigger what your saying is that I will most likley be sending a lot less than peak voltage to the OT12's to balance the bass and tops?


And correct me if im wrong a 6db gain equateds to double the sound level, i.e double spl
And that being said if the max volatge on using one channel on the QSC 1400 per sub 8ohms 270 watts = 46Volts and 50V being the limit for the lab12 that 4V less is equal to what interms of db. I saw sinewave some where calculate this, but cant find it again.

Sorry mate,
I was just trying to say that the voltage limit for the Otops should be much the same as the DR series cabs, with overall response from the Otops being 1-2 dB lower. Not terribly significant. Just stay with 38-40V.

Yes, source first, mixer second.
3 and 3.5 depend on what you buy. The DBX driverack is all that in one unit.
If you go the DEQ/DCX way, then I use EQ (ie the DEQ 2496) first and crossover/DSP/limiter (DCX 2496) next in the chain.
Then amps, then cabs.

Now the amp thing.
Ok, you can get 46V out of your amp, but you haven't limited yet! Just remember that limiting is stopping transients.
So then it depends on what you buy as DSP etc as to your limiting increments.
For the DBX it's in 3 dB increments IIRC, for the DCX it's 1 dB increments.
So, you have to calculate the decrease of your amps maximum output by whatever your minimum limiting increment is (ie 3dB or 1 dB). Hope that makes sense...

[biggerrigger]

The DBX PA+ is able to do .1 DB increments for the limiter. Or maybe it was volts now that I think of it, Either way it is .1

[Michael Murphy]

No worries mate, saw after about the DR comparison driver.

The only reason I mentioned the db voltage thing is that I was trying to quantify what a 4v difference in db is.

Which brings me to the muddy last part

Now the amp thing.
Ok, you can get 46V out of your amp, but you haven't limited yet! Just remember that limiting is stopping transients.
So then it depends on what you buy as DSP etc as to your limiting increments.
For the DBX it's in 3 dB increments IIRC, for the DCX it's 1 dB increments.
So, you have to calculate the decrease of your amps maximum output by whatever your minimum limiting increment is (ie 3dB or 1 dB). Hope that makes sense...

Transients are spikes which could take ur voltage momentarly beyond the max voltage? Correct

An what ur saying is that the limiter can be adjusted to respond to smaller or larger spikes? I thought it was just input in max value and thats it.
So its some thing like a cross over point in terms of 40Hz HP 12db vs 24db vs 48db?

And if so how do you check the limiter setting, crank everything up and make sure nothing greater than 50V leaves the amp?

[Bruce Weldy]

And if so how do you check the limiter setting, crank everything up and make sure nothing greater than 50V leaves the amp?

Exactly. Disconnect the speakers, put a voltmeter across the speaker outputs of the amp, run a test tone through the setup.

After you have your outputs on your board just below the red, set the limiter so that the output doesn't exceed the max voltage.

Then, throw the master fader all the way into the red as far as it will go - the voltage should stay at the limit. If it does, then you have successfully set the limiter.

[Grant Bunter]

Transients and how high they can go are well explained in "protecting your driver" in the plans.

For you, having to engage the limiter to protect from transients simply means you can't give your cabs 46V. If the minimum increment on the driverack is 0.1dB, set it to that and you should get, say 45V. Hope that's clearer.

+1 on Bruce's post

[Michael Murphy]

Grant earlier you mentioned that the Drive rack can do all. Is that the DriveRack 260 you were refering too. Im seeing it on ebay for circa 600US
It can cross, limit and eq. Any one familiar with it know if it is HP and LP for the bass?

[Bruce Weldy]

Is that the DriveRack 260 you were refering too. Im seeing it on ebay for circa 600US
I

Yes, it can do all that....but, the PA, PA+, and the PX can also do it....and they are a lot cheaper.

[Michael Murphy]

Bruce you run the 4ot12 with the 2 t39's ?

[Bruce Weldy]

Bruce you run the 4ot12 with the 2 t39's ?

Yep. But, I'm getting ready to build two more T39s. I'm not doing disco....it's a live band rig. It works good, but two more will help with the bigger outside gigs.